FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
c93.c
Go to the documentation of this file.
1 /*
2  * Interplay C93 video decoder
3  * Copyright (c) 2007 Anssi Hannula <anssi.hannula@gmail.com>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "avcodec.h"
23 #include "bytestream.h"
24 #include "internal.h"
25 
26 typedef struct {
27  AVFrame pictures[2];
30 
31 typedef enum {
39  C93_NOOP = 0x0E,
40  C93_8X8_INTRA = 0x0F,
41 } C93BlockType;
42 
43 #define WIDTH 320
44 #define HEIGHT 192
45 
46 #define C93_HAS_PALETTE 0x01
47 #define C93_FIRST_FRAME 0x02
48 
50 {
51  C93DecoderContext *s = avctx->priv_data;
52  avctx->pix_fmt = AV_PIX_FMT_PAL8;
55  return 0;
56 }
57 
58 static av_cold int decode_end(AVCodecContext *avctx)
59 {
60  C93DecoderContext * const c93 = avctx->priv_data;
61 
62  av_frame_unref(&c93->pictures[0]);
63  av_frame_unref(&c93->pictures[1]);
64 
65  return 0;
66 }
67 
68 static inline int copy_block(AVCodecContext *avctx, uint8_t *to,
69  uint8_t *from, int offset, int height, int stride)
70 {
71  int i;
72  int width = height;
73  int from_x = offset % WIDTH;
74  int from_y = offset / WIDTH;
75  int overflow = from_x + width - WIDTH;
76 
77  if (!from) {
78  /* silently ignoring predictive blocks in first frame */
79  return 0;
80  }
81 
82  if (from_y + height > HEIGHT) {
83  av_log(avctx, AV_LOG_ERROR, "invalid offset %d during C93 decoding\n",
84  offset);
85  return AVERROR_INVALIDDATA;
86  }
87 
88  if (overflow > 0) {
89  width -= overflow;
90  for (i = 0; i < height; i++) {
91  memcpy(&to[i*stride+width], &from[(from_y+i)*stride], overflow);
92  }
93  }
94 
95  for (i = 0; i < height; i++) {
96  memcpy(&to[i*stride], &from[(from_y+i)*stride+from_x], width);
97  }
98 
99  return 0;
100 }
101 
102 static inline void draw_n_color(uint8_t *out, int stride, int width,
103  int height, int bpp, uint8_t cols[4], uint8_t grps[4], uint32_t col)
104 {
105  int x, y;
106  for (y = 0; y < height; y++) {
107  if (grps)
108  cols[0] = grps[3 * (y >> 1)];
109  for (x = 0; x < width; x++) {
110  if (grps)
111  cols[1]= grps[(x >> 1) + 1];
112  out[x + y*stride] = cols[col & ((1 << bpp) - 1)];
113  col >>= bpp;
114  }
115  }
116 }
117 
118 static int decode_frame(AVCodecContext *avctx, void *data,
119  int *got_frame, AVPacket *avpkt)
120 {
121  const uint8_t *buf = avpkt->data;
122  int buf_size = avpkt->size;
123  C93DecoderContext * const c93 = avctx->priv_data;
124  AVFrame * const newpic = &c93->pictures[c93->currentpic];
125  AVFrame * const oldpic = &c93->pictures[c93->currentpic^1];
126  GetByteContext gb;
127  uint8_t *out;
128  int stride, ret, i, x, y, b, bt = 0;
129 
130  c93->currentpic ^= 1;
131 
132  if ((ret = ff_reget_buffer(avctx, newpic)) < 0)
133  return ret;
134 
135  stride = newpic->linesize[0];
136 
137  bytestream2_init(&gb, buf, buf_size);
138  b = bytestream2_get_byte(&gb);
139  if (b & C93_FIRST_FRAME) {
140  newpic->pict_type = AV_PICTURE_TYPE_I;
141  newpic->key_frame = 1;
142  } else {
143  newpic->pict_type = AV_PICTURE_TYPE_P;
144  newpic->key_frame = 0;
145  }
146 
147  for (y = 0; y < HEIGHT; y += 8) {
148  out = newpic->data[0] + y * stride;
149  for (x = 0; x < WIDTH; x += 8) {
150  uint8_t *copy_from = oldpic->data[0];
151  unsigned int offset, j;
152  uint8_t cols[4], grps[4];
153  C93BlockType block_type;
154 
155  if (!bt)
156  bt = bytestream2_get_byte(&gb);
157 
158  block_type= bt & 0x0F;
159  switch (block_type) {
160  case C93_8X8_FROM_PREV:
161  offset = bytestream2_get_le16(&gb);
162  if ((ret = copy_block(avctx, out, copy_from, offset, 8, stride)) < 0)
163  return ret;
164  break;
165 
166  case C93_4X4_FROM_CURR:
167  copy_from = newpic->data[0];
168  case C93_4X4_FROM_PREV:
169  for (j = 0; j < 8; j += 4) {
170  for (i = 0; i < 8; i += 4) {
171  int offset = bytestream2_get_le16(&gb);
172  int from_x = offset % WIDTH;
173  int from_y = offset / WIDTH;
174  if (block_type == C93_4X4_FROM_CURR && from_y == y+j &&
175  (FFABS(from_x - x-i) < 4 || FFABS(from_x - x-i) > WIDTH-4)) {
176  avpriv_request_sample(avctx, "block overlap %d %d %d %d\n", from_x, x+i, from_y, y+j);
177  return AVERROR_INVALIDDATA;
178  }
179  if ((ret = copy_block(avctx, &out[j*stride+i],
180  copy_from, offset, 4, stride)) < 0)
181  return ret;
182  }
183  }
184  break;
185 
186  case C93_8X8_2COLOR:
187  bytestream2_get_buffer(&gb, cols, 2);
188  for (i = 0; i < 8; i++) {
189  draw_n_color(out + i*stride, stride, 8, 1, 1, cols,
190  NULL, bytestream2_get_byte(&gb));
191  }
192 
193  break;
194 
195  case C93_4X4_2COLOR:
196  case C93_4X4_4COLOR:
197  case C93_4X4_4COLOR_GRP:
198  for (j = 0; j < 8; j += 4) {
199  for (i = 0; i < 8; i += 4) {
200  if (block_type == C93_4X4_2COLOR) {
201  bytestream2_get_buffer(&gb, cols, 2);
202  draw_n_color(out + i + j*stride, stride, 4, 4,
203  1, cols, NULL, bytestream2_get_le16(&gb));
204  } else if (block_type == C93_4X4_4COLOR) {
205  bytestream2_get_buffer(&gb, cols, 4);
206  draw_n_color(out + i + j*stride, stride, 4, 4,
207  2, cols, NULL, bytestream2_get_le32(&gb));
208  } else {
209  bytestream2_get_buffer(&gb, grps, 4);
210  draw_n_color(out + i + j*stride, stride, 4, 4,
211  1, cols, grps, bytestream2_get_le16(&gb));
212  }
213  }
214  }
215  break;
216 
217  case C93_NOOP:
218  break;
219 
220  case C93_8X8_INTRA:
221  for (j = 0; j < 8; j++)
222  bytestream2_get_buffer(&gb, out + j*stride, 8);
223  break;
224 
225  default:
226  av_log(avctx, AV_LOG_ERROR, "unexpected type %x at %dx%d\n",
227  block_type, x, y);
228  return AVERROR_INVALIDDATA;
229  }
230  bt >>= 4;
231  out += 8;
232  }
233  }
234 
235  if (b & C93_HAS_PALETTE) {
236  uint32_t *palette = (uint32_t *) newpic->data[1];
237  for (i = 0; i < 256; i++) {
238  palette[i] = 0xFFU << 24 | bytestream2_get_be24(&gb);
239  }
240  newpic->palette_has_changed = 1;
241  } else {
242  if (oldpic->data[1])
243  memcpy(newpic->data[1], oldpic->data[1], 256 * 4);
244  }
245 
246  if ((ret = av_frame_ref(data, newpic)) < 0)
247  return ret;
248  *got_frame = 1;
249 
250  return buf_size;
251 }
252 
254  .name = "c93",
255  .type = AVMEDIA_TYPE_VIDEO,
256  .id = AV_CODEC_ID_C93,
257  .priv_data_size = sizeof(C93DecoderContext),
258  .init = decode_init,
259  .close = decode_end,
260  .decode = decode_frame,
261  .capabilities = CODEC_CAP_DR1,
262  .long_name = NULL_IF_CONFIG_SMALL("Interplay C93"),
263 };